1. Technical Field of the Invention
The present invention generally relates to burst switching networks. More particularly, and not by way of any limitation, the present invention is directed a scheduling method for burst switching networks.
2. Description of Related Art
In burst switching technology, such as, in particular, optical burst switching (“OBS”) technology, data bursts, each of which is made up of multiple packets, are switched optically at core nodes, or routers, in the OBS network. Assuming the data bursts are not buffered, the core node must have advance information on the data bursts to configure the switch. To provide this information, a small control packet, called the Burst Header Packet (“BHP”) travels an offset time ahead of the data burst. The BHP includes information on when the data burst will arrive, the destination of the data burst, etc.
Contention may occur between multiple data bursts attempting to traverse the same egress link. Several distributed scheduling algorithms with different behaviors and complexities have been suggested for use in OBS networks. For example, the First-Fit, Horizon, an Horizon with Void Filling algorithms are among the most widely used technique. All of these techniques employ a similar contention resolution criterion based on dropping the data burst which has arrived latest. These techniques only consider data bursts in contention during one time slot. OBS network performance can be defined in terms of burst loss ratio, which is the percentage of bursts lost during scheduling. These existing scheduling algorithms are inefficient and result in high burst loss ratio in OBS systems since for example, the latest arriving data burst may be the longest data burst in contention.
Recently, some have proposed using variations of a contention resolution scheme known as segmentation along with the Horizon Void Filling algorithm to reduce burst packet dropping and improve bandwidth enforcement. Segmentation involves only dropping the portion of the latest arriving data burst which is in contention with other data bursts. This technique requires a complex data burst assembly and disassembly implementation process.
Therefore, what is needed is a contention resolution technique that reduces burst loss ratio in OBS networks.